The argillaceous nature of unconventional gas reservoirs presents ultra-complex lithology, nano-scale porosity and permeability. Petrophysical and mineralogical evaluation of these formations challenge high resolution diversified evaluation techniques to investigate first the dual storage mechanisms of natural gas and later to help in designing hydraulic fracturing techniques for maximum recovery of gas. Research work and contents in this paper are intended to develop some insight about post depositional diagenetic events in shale gas formations which have direct impact on brine evaluation in these types of overly clay rich reservoirs. Insights will help in understanding, reasons of uncertainties and doubts about controversial application of true formation resistivity (Rt) values from resistivity wireline logs in seconds Archie�s (1942) Equation in shale gas reservoir. Direct evaluation and assessment of porosity in shale is not reliable from wire-line logs alone; thus, it is essential that logs be calibrated with lab direct measurements such as QEMSCAN, XRD, and FIB/SEM. In the following sections, the geological background of study area is first discussed followed by our literature review and methodology used to determine different parameters for water saturation evaluation. Results are presented with the sensitivity study of different parameters. Some conclusive results are given at the end. © EAGE Reservoir Geoscience Conference, ResGeo 2018. All rights reserved.